Process of stanching and consolidating porous masses



Patented Jon. 7, 19 41 PATENT orrlcs PROCESS OF STANCHING.AND CONSOLI- DATING roaous Masses Charles Longer, Paria France vNo Drawing. Application August 27, 1931, Serial IWQJGLIM. In'Switaeriand May 25. 1937 some. (01. 81-36) The present invention relates to the treatment of porous masses for the purpose of con-- solidating them and rendering them impermeable. Masses capable of being treated in accordance with this invention include soils, iissured rocks,

porous masonry or concrete and the like. According'to this. invention, one injects into such masses 9. single solution containing sodium silicate, acid and at least one soluble metallic salt in such proportions thata silicic acid gel will be formed alter a controllable lapse of time. Q have discovered that such control can be eifected by varying the proportions oLthese ingredients. Thus the requirements of any situation may be 16 met.

It is known that soluble metal salts act as strong coagulants on water-glass causing the precipitation from the colloidal solution of. silicic acid gel. It is impracticable, however, to use a 20 solution of water-glass and a strong coagulant for purposes of injection because the precipitation is immediate and it is not possible to inject the precipitate into the fine pores of the materialwhich a a desired to consolidate. a has; there; fore, been proposed to inject solutions containing 1 an additional substance which functions to pre vent coagulation. whicln substance necessarily had tube removed in order to bring about coagulation. Such removal wouldbe efiected, for example, by means of a second injection of a gas oranother solution. Another proposal has been to inject a single solution of water-glass and a' slow-acting weak coagulant. This method, however, fails to bring about the desiredsolidifying action.

Where theproduction of the gel has. been accomplished by the injection of two different substances, dependence is placed upon a reaction in situ which depends upon contact between the 40 substances separately injected. Since it is impossible to assure complete mixing of the two substances within a porous mass there is no as-' surance that the spaces within the mass will be uniformly filled with the gel. In thecase where. gas is injected to produce coagulation, it is at'- tended with the disadvantagethat gas-filled voids are produced which weaken the. mass intended,

form silicic acid gel within a definite period, of i time which is capable of being accurately regu lated. In this solution it is possible to use a strong coagulant which will produce a uniform homogeneous gel. The solution is water-clear, extremely .fluid and contains no sediment or precipitate which willhamper the ,process of injection. The solution is moreover substantially diluted and is consequently much more economical than the concentrated solutions heretofore used. The low viscosity of the solution enlarges the radius of action and increases the uniformity of 10 impregnation. It also widens the field of application for the reason that it is capable of being i used in the treatment of masses in which the pores are of very small dimension. I'he present invention, as distinguished from 15 prior processes, can be used for consolidating salty soils such as soils near bodies of salt water. with prior processes the-salt solution in the soil brings about immediate coagulation of the silicate solution, thus preventing proper penetration of the 20 solution. According to this invention, the pH- value of the solution used can be adjusted to counteract the alkalinity of-the soil and thus permit complete control of, the impregnation.

In accordance with the invention, the solution 26 consists of water-glass and a reactive agent com-' prising an acid and a strong coagulant.

I In the present process the, existing pH-value of thesodium silicate is decreased by the addition of an acid in order to obtain a weaker alkaline solution. By further adding a suitable salt of a heavy metal (iron, copper, lead, zinc and the like) as an electrolyte, the latter solution is de-x stroyed' and coagulates to a gel. By decreasing" the pH-value the sodium silicate solution becomes more sensitive and the coagulation to a gel in' the ground or other mass being treated two monthsat room temperature. The present process has been applied practically, and I cite here two; examples: A fine quicksand soil been consolidated according to the present process,- fior the of faciliating "excavation for the foundation work of a water'puriflcation plant. The quicksand had the following grain-distribution: 80% of the particles were smaller than 0.11 mm., 50% smaller than 0.098 mm., 30% smaller than 0.09 mm. and (10% smaller than 0.076 .mm. -The permeability of the sand, at a temperature of 15 C.,

was k=9.1 10- cm. min. The injected solution consisted of industrial sodium silicate or waterglass, of 36 B; diluted with an equal amount, by weight, ofwater, to which solution was added a reactive agent consisting of hydrochloric acid and copper sulphate, in the proportion of two parts by volume of sodium silicate solution to one part by volume of the said reactive agent. The

injected solution after about 47 minutes coagu-" lated in the ground to a silicic acid gel.

The reactive agent of hydrochloric acid and copper sulphate,.reierred to in the foregoing exa cylindrical zone as well as a base plate was consolidated, in' order to avoid a flow of the remaining sand during the excavation. The outer zone of injection, 1. e. the ground covered by the outer row oi injection pipes, initially was subjected to only slight pressure (0.5 atm. gauge at the beginning and 3-4 atm. gauge at the end). The pressures in the inner zone of injection after a short time amounted to 7-8 atm., i. e. the

- ground'here oilered a great resistance to these injections due to the preceding treatment.

In this manner the foundation was carrieddown to about 50 feet below ground-water 'level and the work done in the dry without caissons and without the use of special pumps. a

The second example refers to the comolidating and rendering impermeable of :very porous concrete test specimens taken from a dry dock. The concrete the latter, deteriorated by the action of the seawater, before the treatment showed a permeability of about '1 10-= cm. second. The above mentioned solution was injected under an average pressure. The concrete after treatment showed a permeability of about 1 10 cm. per second under a pressure of atm. gauge.

The amount of acid added to the water-glass vsolution, asa part of the reactive agent, so atfacts the stabilityoi the solution that by means oi. the salt in the reactive agent, acting as a coagulator, a uniform homogeneoussilicic acid gel is obtained after the lapse of a period subject to precise regulation. v

It will readily be understood that by regulating the amount of agent the solution may be caused to gel at such time after its injection as may be desired. In a case where underground conditions are encountered which tend to carry away the injected solution it may be adjusted to gel very rapidly. Or 11', for example, it is desired to allow the solution to penetrate through the soil or other mass for a considerable distance, its time of setting may besuitably delayed.

What I claim and desire to secure by Letters Patentis:

1. A.process for consolidating and rendering impermeable pervious soils, fissured-rock, masonry, concrete and the like which comprises introducing into the mass to be treated a single solution consisting of a mixture of water-glass with a reactive agent comprising an acid and a soluble salt of a heavy metal, the proportion of said agent to the water-glass being such that a silicic acid gel is formed in situ after a delay suflicient to permitthe desired impregnation oi the mass.

2. A process for consolidating and rendering impermeable 'pervious soils, fissured-rock masonry, concrete and the like which comprises introducing into the mass to be treated a single solution containing a colloidal alkali silicate solution capable oi being coagulated to form a silicic acidv gel, a reactive agent for coagulating the solution containing a heavy metal salt as coagulant and an acid for delaying the coagulation, and regulating the time of coagulation by adjusting the proportion of said agent to the water-glass.

3. A process of treating masses of porous material to consolidate them and render themimpermeable which comprises introducing into the,

CHARLES LANGER. 

